Diffusion-controlled kink motion

A simple model for the growth of kinks by volume diffusion is discussed, and singular perturbation methods, valid for supersaturations much less than one, are used to derive coupled integral equations for the motion of trains of (well-spaced) kinks. Numerical results are presented for the motion of two-and three-kink trains. This paper is based on a presentation made in the symposium “The Role of Ledges in Phase Transformations” presented as part of the 1989 Fall Meeting of TMS-MSD, October 1–5, 1989, in Indianapolis, IN, under the auspices of the Phase Transformations Committee of the Materials Science Division, ASM INTERNATIONAL.     

THE REAL MEANING OF STRATEGIC PLANNING

The strategic part of strategic planning often allows for a variety of interpretations of its true meaning. When preparing IS strategic plans, it is especially important for IS and senior managers to have the same, clear definition of the word so that their strategic plan is indeed just that.     

Effects of daytime ingestion of melatonin on short-term athletic performance

The immediate effects of ingesting melatonin in the daytime include decreased alertness and body temperature. To date, no researcher has examined whether daytime ingestion of melatonin leads to impairments in variables relevant to short-term (<10 min) athletic performance. Twelve physically active participants (mean +/- s age = 25.2 +/- 5.0 years, body mass = 81.4 +/- 12.1 kg and chronotype = 33.8 +/- 6.3 units) ingested 5 mg of melatonin or placebo at 11:45 hours in a double-blind experiment. At 13:00 and 17:00 hours, subjective alertness was measured, together with intra-aural temperature, reaction time (two-, four- and eight-choice), short-term memory recall and grip strength. Performance, ratings of perceived exertion (RPE) and heart rate were also recorded during a 4-km cycling time trial. At 13:00 hours, the mean +/- s intra-aural temperature was 0.49 +/- 0.79 degrees C lower after ingestion of melatonin than after placebo (p = 0.015), but this difference was not apparent at 17:00 hours. At both 13:00 and 17:00 hours, melatonin reduced (p < 0.05) alertness, short-term memory and exercise heart rate by 1.5 +/- 1.8 units, 1 +/- 1 digits and 6 +/- 9 beats.min(-1), respectively (mean +/- s). Eight-choice reaction time was also slower at both times of day after ingesting melatonin. Melatonin did not influence time trial performance or RPE (p > 0.05). The effects of 5 mg of melatonin seem more pronounced for mental rather than physical components of short-term athletic performance, although the cardiovascular responses to exercise are affected. Some effects of melatonin were apparent 5 h after ingestion when the hypothermic effects of melatonin had dissipated.     

Contributing factors in construction accidents

This overview paper draws together findings from previous focus group research and studies of 100 individual construction accidents. Pursuing issues raised by the focus groups, the accident studies collected qualitative information on the circumstances of each incident and the causal influences involved. Site based data collection entailed interviews with accident-involved personnel and their supervisor or manager, inspection of the accident location, and review of appropriate documentation. Relevant issues from the site investigations were then followed up with off-site stakeholders, including designers, manufacturers and suppliers. Levels of involvement of key factors in the accidents were: problems arising from workers or the work team (70% of accidents), workplace issues (49%), shortcomings with equipment (including PPE) (56%), problems with suitability and condition of materials (27%), and deficiencies with risk management (84%). Employing an ergonomics systems approach, a model is proposed, indicating the manner in which originating managerial, design and cultural factors shape the circumstances found in the work place, giving rise to the acts and conditions which, in turn, lead to accidents. It is argued that attention to the originating influences will be necessary for sustained improvement in construction safety to be achieved.     

Effect of heat treatment on properties of thixoformed high performance 2014 and 201 aluminium alloys

Tempering treatments T4, T5 and T6 have been applied after thixoforming to investigate the effects of heat treatment on microstructure and mechanical properties of thixoformed wrought aluminium alloy 2014, a modified 2014 and high strength casting aluminium alloy 201. The modified 2014 was a simplified version of 2014 with composition (wt%) Cu 3.87, Mg 0.6 and Si 0.14. The results showed that standard solution time for conventional wrought alloy 2014 (1 h at 500°C) gave incomplete homogenisation of thixoformed material. Longer times (5 and 17 h) at 500°C are required for complete solutionisation of CuAl₂. Low hardness values in the as-thixoformed 2014 were increased by subsequent heat treatment. After 18 h ageing at 160°C, the hardness of material solutionised for 5 and 17 h is higher than that for the standard 1 h. The tensile properties of the thixoformed 2014 were improved and close to those of forged 2014 using optimised post-forming heat treatment (solution treatment for 17 h at 500°C followed by water quenching and then ageing for 24 h at 160°C). Thixoformed alloy 201 in the standard T6 condition (2 h at 513°C followed by 17 h at 527°C and water quenching and then ageing 20 h at 153°C) showed a significant improvement over permanent mould casting. Good elongation to fracture (19.6%) was found for thixoformed modified 2014 in the T6 condition.     

CRACK INTERACTION, COALESCENCE AND MIXED MODE FRACTURE MECHANICS

Abstract— Multiple cracks are often observed in engineering structures; and their interaction and coalescence may significantly affect the lifetime of component or structure. In this paper, the general features associated with crack interaction and coalescence are presented, and the conditions for coalescence in various forms are reviewed. A model has been developed based on the principles of mixed mode fracture mechanics, to provide a rational explanation for the phenomenon of crack interaction and to predict the coalescence conditions. The latter is found to agree reasonably with the experimental observations.     

Advanced optical and magneto-optical recording techniques: a review

Optical data storage is advancing rapidly as we move forward in the 21st Century. Most people today are familiar with CDR and CD-RW as forms of optical data storage, but DVD-R, with considerably higher capacity, will challenge CD-R as the preferred storage medium soon. This review paper looks at the current state of optical recording and some of the current techniques which offer increased magneto-optical storage density, such as Magnetic Super Resolution (MSR), which is already on the market as the GIGAMO disk, and other methods under development. The latter includes Magnetically AMplified Magneto-Optical System (MAMMOS) and Domain Wall Displacement Detection (DWDD). To complement these technologies are a variety of optical techniques, such as near-field recording, which will enable higher storage densities by overcoming the diffraction limit. Holographic storage has promised much over the years, and has largely remained in the research domain. However, new materials and multiplexing techniques show considerable promise for this volumetric storage medium. The overlapping optical and magneto-optical technologies have yielded the concept of hybrid recording and this will also be addressed in this paper. The paper concludes with a look at alternative storage mechanisms, which utilise electronic, as opposed to thermal transitions, to offer improved data rates and improved storage efficiency, and this may dramatically change the way data is stored.David Jenkins would like to thank the Royal Academy of Engineering for financial assistance for attending the Information Storage and Processing Systems Conference where this paper was presented. Paper presented at the 13th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 17–18 June, 2002     

Systematic stereotype usage

As one of the UMLs main extension mechanisms, stereotypes play a crucial role in the UMLs ability to serve a wide and growing base of users. However, the precise meaning of stereotypes and their intended mode of use has never been entirely clear and has even generated significant debate among experts. Two basic ways of using UML stereotypes have been observed in practice: One to support the classification of classes as a means of emulating metamodel extensions, the other to support the classification of objects as a means of assigning them certain properties. In this paper we analyze these two recognized stereotype usage scenarios and explain the rationale for explicitly identifying a third form of usage scenario. We propose some notational concepts which could be used to explicitly distinguish the three usage scenarios and provide heuristics as to when each should be used. Finally, we conclude by proposing enhancements to the UML which could support all three forms cleanly and concisely.     

Comparison of mineral and soluble iron Fenton's catalysts for the treatment of trichloroethylene

Contaminant degradation, stoichiometry, and role of hydroxyl radicals (OH*) in four Fenton's systems were investigated using trichloroethylene (TCE) as a model contaminant. A standard Fenton's system, a modified soluble iron system with a pulse input of hydrogen peroxide, and two modified mineral-catalyzed systems (pH 3 and 7) were studied. In the standard Fenton's system, which had the most efficient reaction stoichiometry, 78% of the TCE was degraded; however, chloride analysis indicated that no more than two of the three chlorines were displaced per TCE molecule degraded. Although the modified soluble iron system was characterized by 91% TCE degradation, chloride analysis also indicated that no more than two of the chlorines were lost from the TCE. In the goethite system of pH 3, > 99% of the TCE was degraded. Near-complete release of chloride suggested that the TCE may have been mineralized. Only 22% degradation of TCE was achieved in the pH 7 goethite system. and there was minimal release of chloride. The mineral-catalyzed reactions exhibited the least efficient reaction stoichiometry of the four systems. Experiments using hydroxyl radical scavengers showed that the standard Fenton's system degraded TCE entirely by hydroxyl radical mechanisms, while approximately 10-15% of the degradation achieved in the modified soluble iron and goethite-catalyzed systems at pH 3 was mediated by non-hydroxyl radical mechanisms. In the goethite system at pH 7, only non-hydroxyl radical mechanisms were found. The goethite-catalyzed system at pH 3 effectively degraded the parent compound and may have the potential to mineralize contaminants when used for in situ soil and groundwater remediation and ex situ waste stream treatment in packed-bed reactors.     

Phenotypic characterisation of the dendritic cell infiltrate in prostate cancer

4-Nitrocatechol was identified as a product of transformation of 4-nitrophenol by bacterial strain Corynebacterium sp.8/3 using direct acetylation of biodegradation samples by acetic anhydride followed by GC-MS analysis. The identity of 4-nitrocatechol, in the form of diacetate, was confirmed by electron-impact spectra and spectra recorded under chemical ionization conditions (positive and negative modes). Negative-ion chemical ionization was used for quantification of 4-nitrocatechol in biodegradation samples in a concentration range of 1-25 mg/l.